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Testing Old Tapes To Save Them
JMarshall writes: Recordings on old audio tapes won't be worth much in another 20 years, and some are already too degraded to play. A team including members from the Library of Congress report that infrared spectroscopy can noninvasively separate magnetic tapes that can still be played from those that can't, without risking the tapes by sticking them in a player. Unplayable tapes can sometimes be rescued by heating, which can make them playable for long enough to digitize. This method could help archivists identify which tapes need special handling before they get any worse.
Memory chips.
The ROM's on early-80's consoles are still, on the whole, perfectly readable (as evidenced by MAME), and they don't even TRY to use error correcting codes to ensure resiliency.
I have CompactFlash of some vintage and it's all still perfectly readable. Even hard drives are quite readable if stored properly and not live for a long time.
I imagine if you really wanted to make something last 20 years and still be readable, a basic EEPROM with I2C-like serial interface will be readable, and you could probably describe a circuit/timing to read from it on the casing of the chip itself with one diagram.
As a MAME developer, I have the sad duty to inform you that this, sadly, is not the case. ROMs for early video games are gradually succumbing to bitrot. EPROMs used in arcade games eventually leak their trapped charges, and mask layers oxidise in mask ROMs. Flash ROMs from newer arcade games can degrade in as little as 15 years. If you're lucky you can get a good read by heating the chip up or cooling it down. But in many cases the data is permanently lost.